Method of storing and vaporizing liquefied gases



Nov. 29, 1949 G. R. BENZ METHOD OF STORING AND VAPORIZING LIQUEFEEDGASES Fiied Feb. 11, 1946 IIIIIIIIIIII *IIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIII INVENTOR G. R. BENZ ATTORNEYSIIIIIIIIIIIIIIIII\ o I I [III] I.

IIIIIIIIII III/II Patented Nov. 29,, 1949 George R. Ben2 Baittlesville,Okla, assigno'r to Phillips Petroleum company, a corporation of DelawareApplication-February 11, 1946, Serial No. 64634 7 1) claims (Cl. e2 1)This invention relates to the storage and vaporization of liquefiedgases. In one of its more specific aspects it relates to a method ifolthe storage of liquefied etroleum gases wherein the liquefied gas ismaintained at a relatively'low temperature to facilitate storage.

Because of their high vapor pressure at "atmospheric temperature,liquefied gases such "as liquefied petroleum gases require high pressurestorage vessels or low pressure insulated storage vessels plusrefrigeration to keep the stored ma= t'erial in the liquid state untilneeded for use in the gaseous form. investment in storage equipment andcost of vaporization of these gases, particularly in large industrialand utility company installations, are therefore major ite'iiis ofexpense.

One object of my invention is to provide a low cost method of storage ofsuch liquefied gases using low pressure insulated tanks in place "ofthenormauy used high pressure uhinsulated vessels.

Another object of my invention is :to provide for low pressure storageapparatus wherein vaporization unit permits uniformity 'ifijfiiiaflitior vaporized gas from a mixture of-stored Still another object 6f 'fn'yint/en is provide a vaporization unit in "conjunction "with the storagevessel wherein the seneib e heat of the stored liquid is 'utiliZedforits vaporization.

Still other objects andadvantages of my m vention will be apparent tothose skilled the art from a careful study of the following *d scriptionand drawing which respectively de scribes and illustrates preferredembodiments of my invention.

In the drawing, Figure 1 illustrates one form of my storage andvaporization apparatus par ticularly adapted to the storage and"vaporiza- 'tion of either individual hydrocarbons or mix' 'tures ofnormally gaseous hydrocarbons;

Figure 2 illustrates a second or my invention which is especiallyadapted to the storage and vaporization of a single gaseous hydrocarbon.

Referring now to the drawing espeeiauy to Figure 1, a tank assembly H iscomposed or an inner steel shell or tank I21 and an exterior" insulationl3. The tank is equipped with roar inlet or outlet lines I4, l5, l6 and26. Pumps 24 and 3| are for transfer of liquefied gas while a vaporizerI8 is used for transforming the :Iique fied gas into its normallygaseous form, and

a pressure regulator 22 controls final outletprese sure. I9 and 2| areheat exchangers.

In the operation of the embodiment of Figure is therefore nearly alwaysavailable.

:1, a lidu'efi'ed petroieum gas sueh as propane butane -or a mixture ofthese ease under suine'ieht pressure to that they are nouns at xistingtemperature, be pumped into the tankassrhbly I'Ifthroii'gh i'n1et lineit from any soureeyfor examples transport triick teak Because or theirhig vapor pressure if these hydrocarbons stored at 'a'tiiiosphe"temperature thick Walled high pressure vessels are required. I proposeto 'eo'oi these high vapo pressure hqiiids so that they may be stored at(TOTl'Sldf'ablY IOWl DYES'SQTBS.

Iii relatively large installations, such as required by puhiie'iitilities or in industrial installatio s, considerable heat isabsorbed, or 6onverse1y, considerable cooling is available when theseiieuei'ied gases are vaporized for plant utility use. I make 1156 (ifthis available (tooling for maintaining the liquefied gas in the storagetank H at a low t mperature. h

Ifl' lltllity and industrial installations liquefied gas is most always"continuously removed, Va poriz'ed and passed to the gas mains fortraifs= portation t0 'pOiI lliS bf COnS'll'lllptiql'l, and 'C'OfillhgFor trans; fer to'a gas main, as for example line '40, liquid is passedthrough all outlet lill l6 and through 9L lifi IT a vaporizer l3. Fromthis fileblla'e iii sm the hydrocarbon which is cooled in theVQDDriZLtifiifl "Slifi through VQ'Jf OIiZT 18, passes through line Hilil'i'ti 6116 'Eli'd 0f the heat e3;- hfih'gr l9, out the opposite fldafld througlitli fillii'illafy heater 2], 2 3 and fil's'slif'e lg lll-IERTI 2 2 and fifillly H1110 the g aS 'lriail'l 4U. W A-fl additibllaland relatively large Cillaiflliifiy 5f liiliiefid gas is Witlldlawfifrom the storage vessel ll through the outlet line l5, and underpressure from a pump '21 passes on through a line as through the heatexchanger 59 in indirect heat exchange with the above mentioned cooledgas, and through a transfer line '26, is passed back into the storagetank ll. In this manner sensible heat frbiil the liquefied passingthrough the exchanger it from line 25 furnishes heat for the evaporationof the 1io'uelied gas passing through the exehahgei' -fr'orri evaporator18 and line I'll Liquid then emerging from the exchanger" iihe is haseeeiieooi'ed.

and this cooled liquid then passes on into the main storage vessel H. '1

By continuously operating in this manner the body of liquid in vessel His appreciably cooled and since the vessel is intended to be wellinsulated the liquid, once cooled, will remain cool for considerableperiods of time even during warm summer days.

Since the latent heat of evaporation of a compound or mixture ofcompounds is so much greater than the specific heat of the correspondingmaterial, I have found that by operating a system in the manner justdescribed, the liquefied gas in storage may be cooled to quite a lowtemperature and maintained at that low temperature with comparativeease.

I have further found especially under heavy vaporization load conditionsthat the liquid in the storage vessel may be cooled to such an extentthat the stream passing through line 25 to the exchanger |9 will notcontain sufiicient sensible heat to complete the vaporization of thematerial passing through line I! into the exchanger. Under theseconditions line 20 may then contain some vapor or gas and some liquidand to complete the vaporization I have provided the auxiliary heatexchanger 2|. I am able to use hot water or steam as a hot heat exchangemedium for passing from line 38 into this latter exchanger and outthrough line 39. By supplying extraneous heat in this manner thehydrocarbon gas passing from this exchanger in line 23 is fullyvaporized and ready for pressure reduction to gas main pressure in theregulator 22.

In the event that it is desired to maintain the pressure and temperatureof the product in the storage vessel I I as low as possible or near tothe normal boiling point of the hydrocarbon stored, it may then benecessary to operate a pump 3| by closing valve 32 in line I! andopening valves 33 and 34. Under these conditions liquid from tank I Iwill pass through line I6, line 35, valve 33, pump 3|, valve 34 and line35 into the regulator or vaporizer I8 and exchangers i9 and 2| forcomplete vaporization. It will, of course, be necessary under suchconditions to supply that amount of heat not supplied from the sensibleheat of the product in storage by steam or hot water through theconnections 38 and 39 on the exchanger 2| in order to secure final andcomplete vaporization of the gas prior to passing through the regulator22 into the gas main.

In order to handle varyin requirements for gas from the system the backpressure regulator 22 is used to permit flow of gas from the exchanger2I to the gas main 4|) as the pressure on the downstream side ofregulator 22 tends to decrease. In this manner pressure on the systemupstream of this regulator is accordingly held at least to pounds persquare inch greater than on the downstream side. When using regulator 22with pump 3|, an excess of liquid hydrocarbon builds up between pump 3|and said regulator. The excess hydrocarbon liquid will enter therecirculation system through line 36. this excess liquid put out by pump3| will merely pass through line 35, regulator 31, line 25, exchanger 9,line 26 into the storage vessel I I.

Regulator 31 may be set at a pressure 10 to 20 pounds per square inchgreater than the setting of regulator 22 so that there will always be apotential supply of liquefied gas ready to be vaporized for passage intothe gas main 40.

In case the liquefied petroleum gas in storage tank I I is oneindividual hydrocarbon, as for example, butane or propane, then theapparatus illustrated in Figure 2 of the drawing may be used. Underthese special conditions it may well be advaniageous to use this flowplan since such apparatus is very simple, and less expensive to in- Thusstall and to operate than the apparatus of Figure 1.

When employing a single hydrocarbon, there cannot be a change incomposition of the liquefied gas during evaporation from a body of theliquid. Thus, the liquefied gas may be transferred from a tank car ortransport truck, not shown, through a line 55 into a storage tank 5!.This tank may be similar in all respects to tank I I of Figure l, andmay be composed of steel walls 52 and a layer of insulation 53. Anauxiliar tank or evaporator 54 may be of similar construction as tank 5|and accordingly composed of steel wall 55 and insulation 56.

A line 57 conveys liquefied gas from storage tank 5| into the evaporatortank 54. A liquid level controller device is installed as shown tooperate a valve 58 for maintenance of a desired liquid level in theevaporator. A line 59 is adapted to convey liquefied gas from evaporator5 to the storage tank 5| by action of a pump 55. A line 6| leading fromthe top of the evaporator 54 conducts vaporized hydrocarbon from thevapor space in said evaporator to a back pressure regulator 62 whichdischarges the gas at a lower pressure to a gas main 53 fortransportation to points of distribution or use.

In this embodiment the pump 69 operates at substantially a constantcapacity and circulates liquid from the evaporator 54 to the storagetank 5|. As the liquid level in the evaporator drops below apredetermined point, the liquid level controller operates to open valve58 and permit entry of liquefied gas from vessel 5|. As the pressure inthe gas main drops below a predetermined gas main pressure, the backpressure controller 62 opens and permits passage of gas from the vaporspace in the evaporator 54 through line 5| into the gas main 63. Whenpressure in the vapor space in the evaporator 54 decreases below acertain point the liquid boils until the pressure increases sufficientlyto cause an increased gas flow through line 6| into the gas main. Thenat a time when the gas main pressure reaches a predetermined value theregulator 62 closes and flow through line 6| stops.

The evaporation of liquid in the evaporator 54 absorbs latent heat ofevaporation and accordingly cools the liquid remaining in the evaporatorso that it is cooled liquid which is pumped through line 59 back intothe storage vessel 5|. In this manner the stored liquid in vessel 5|becomes cooled and remains cool so that its vapor pressure or storagepressure is relatively low, and a less expensive storage vessel may beused.

In either embodiment, once the liquid is cooled, in large installationsor in any installation wherein there is withdrawal of sufilcient gas tomaintain the remaining stored liquid well cooled, then the storagevessels may be of the less expensive low pressure type.

A further advantage of my invention is that a major part of the heat forthe evaporation of the liquid is furnished by the sensible heat of theremaining stored liquid.

The tanks and 5| may be of any shape or form desired, and of anyconstruction desired. They need only to withstand such pressure asresults from the liquefied gas as after being cooled according to myinvention. The tanks I I and 5| and the evaporator 54 of Figure 2 shouldbe well insulated and such type of insulation is well known in theliquefied petroleum gas industry.

The pumps used herein may be any type demeans and may selected fromamong those commercially available, as long as they are ca-- p'a -ble oftransferring cooled liquefied petroleum gases in a satisfactory andeconomic manner.

I The pressure reducer 3 1 and the pressure reducer Vaporizers I8 ofFigure l and the back pressure regulators -22 of Figure "1 and 62 ofFigure 2 may likewise be selected from amon those commercially availableand-suited to the problem at hand.

v In like manner the exchangers l9 and 2| of Figure 1 may beselectedfrom among those available to perform such heat exchange as necessary.Likewise, hot water or steam or other heat exchange medium may beselected as desired for use in the exchanger 21 of Figure l. I

This invention is applicable, not only to the storage of propane orbutane or mixtures of these as mentioned hereinbefore, but may also beused for the storage and vaporization of methane, ethane, as well aspropane and butane, and the corresponding olefins and diole'fins, aswell as mixtures containing practical combinations of these gases.

Valves, safety valves, controllers and other auxiliary devices-as mightbe deemed useful by those skilled in'the art have been omitted forpurposes of simplicity; Only those essential have been shown.

It will be obvious to those skilled in the art that many alterations andvariations of my invention may be made and .yet remain within theintended spirit and scope of my invention.

Having disclosed my invention, I claim:

1. A method for storing and dispensing liquefled gases in a gasdispensingsystem which *comprises withdrawing a portion of saidliquefied gas from the lower portion of a storage vessel and passingsaid portion to a heat exchange zone; vaporizing a first portion of saidliquefied gas therein; removing said vaporized first portion from saidheat exchange zone and passing it to a distribution zone; removing anunvaporized second portion from said heat exchange zone; mechanicallymaintaining said second portion under pressure; and returning saidsecond portion to the upper portion of said storage vessel.

2. A method for storing and dispensing liquefied gas in a gas dispensingsystem which comprises withdrawing a first portion of said liquefied gasfrom a storage vessel and vaporizing said portion; withdrawing a secondand larger portion of liquefied gas from said vessel and mechanicallymaintaining said second portion under pressure;

passing said second portion of liquefied gas in heat exchange relationwith said vaporized first portion in a heat exchange zone, whereby saidsecond portion is cooled; passing said vaporized portion to a gasdistribution zone; and returning said second liquefied gas portion tothe upper portion of said storage vessel.

3. A method of storing and dispensing liquefied petroleum gas in a gasdispensing system which comprises withdrawing a first portion ofliquefied petroleum gas from a storage zone; passing said first portionof liquefied gas through a pressure reducing zone to a primary heatexchange zone; withdrawing a second portion of liquefied petroleum gasfrom said storage zone; passing said second portion of liquefiedpetroleum gas under mechanical pressure through said primary heatexchange zone in indirect heat exchange with said first portion ofliquefied petroleum gas, whereby said second portion is cooled; returninsaid second portion to the upper portion of said storage zone; passingsaid first gas portion through an auxiliary heat exchange zone inindirect heat exchange with a hot fluid heat exchange material whereinadditional vaporization of said first portion of liquefied gas is acconiplished; and passing said vaporized gas portion through a pressurecontrol zone to a gas distribu tion zone.

- 4-. A method of storing and dispensing liquefie petroleum gas in a gasdispensing system which comprises withdrawing a first portion ofliquefied petroleumgas from a storage vessel; passing said first portionof liquefied gas through a pump; whereby pressure is maintained on saidfirst portion; withdrawing a second portion of said liquefied gas fromsaid storage vessel; pumping said second portion under pressure into aprimary heat exchanger; passing a first portion of said first liquefiedgas portion through a pressure re ducer vaporizer and through saidprimary heat exchanger in indirect heat exchange withsaid Second portionof liquefied gas; passing a second portion of said first liquefied gasportion through a pressure regulator into said second liquefied gasportion; passing said second liquefied gas portion through said heatexchanger and returning said portion to the upper portion of saidstorage vessel; passing said first gas portion through an auxiliary heatexchanger in indirect heat exchange with a hot fiuid heatexchangematerial, wherein additional vaporization of said first por tion ofliquefied gas is accomplished; and pass-'- ing said vaporized gasportion through a pressure regulator to a gas distribution zone.

5 A method for storing and dispensing liquefied petroleum gas in a gasdispensing system which comprises withdrawing a portion of saidliquefied gas from a storage vessel and passing said portion to a heatexchange zone; maintaining a predetermined liquid level in said heatexchange zone; vaporizing a first portion of said liquefied gas therein;removing an unvaporized portion from direct heat exchange relation withsaid vaporized portion in said heat exchange zone; mechanicallymaintaining said second portion under pressure and returning it to theupper portion of said storage vessel; and passing said vaporized portionthrough a pressure control zone to a gas distribution zone.

6. A liquefied gas storage and dispensing system comprising an insulatedstorage vessel; a primary heat exchanger; a first conduit communieatingbetween the lower portion of said storage vessel and said primary heatexchanger; a second conduit communicating between the lower portion ofsaid storage vessel and said primary heat exchanger; a pump disposed insaid first conduit intermediate its ends; a pressure reducer vaporizerdisposed in said first conduit intermediate said pump and said primaryheat exchanger; a second pump disposed in said second conduitintermediate its ends; a third conduit communicating between said firstconduit, intermediate said pump and said pressure reducer vaporizer andsaid second conduit, downstream of said pump; a pressure regulatordisposed in said third conduit intermediate its ends; a fourth conduitcommunicating between said primary heat exchanger and the upper portionof said storage vessel, adapted so as to convey fluid from said secondconduit to the upper portion of said storage vessel; an auxiliary heatexchanger; a fifth conduit communicating between said primary heatexchanger and said auxiliary heat exchanger,

adapted so as to convey fluid from said first conduit to said auxiliaryheat exchanger; a heating material inlet and outlet in said auxiliaryheat exchanger; a sixth conduit communicating between said auxiliaryheat exchanger and a gas disposal point, adapted so as to convey gaseousfluid from said fifth conduit to a gas disposal point; and a pressureregulator disposed in said sixth conduit intermediate its ends.

7. A liquefied gas storage and dispensing system comprising an insulatedstorage vessel; 2. primary heat exchanger; a first conduit communicatingbetween the lower portion of said storage vessel and said primary heatexchanger; a pressure reducer vaporizer disposed in said first conduitintermediate its ends; a second conduit communicating between the lowerportion of said storage vessel and said primary heat exchanger; a pumpdisposed in said second conduit intermediate its ends; a third conduitcommunicating between said primary heat exchanger and the upper portionof said storage tank, adapted to convey fluid from said second conduitto the upper portion of said storage vessel; an auxiliary heatexchanger; a fourth conduit communicating between said primary andauxiliary heat exchangers, adapted so as to convey fluid from said firstconduit to said auxiliary heat exchanger; a heating material inlet andoutlet in said auxiliary heat exchanger; a fifth conduit communicatingbetween said auxiliary heat exchanger and a gas disposal point, adaptedso as to convey gaseous fluid from said fourth conduit to a gas disposalpoint; and a pressure regulator disposed in said sixth conduitintermediate its ends.

8. A liquefied gas storage and dispensing system comprising an insulatedstorage vessel; heat exchanger means; conduit means communicatingbetween the lower portion of said storage vessel 8 and said heatexchanger means; a second conduit means communicating between said heatexchanger means and a gas disposal point; a pres sure regulator disposedin said second conduit means intermediate its ends; a third conduitmeans communicating between said heat' e'x changer means and the upperend of said storage vessel, adapted so as to convey liquid from saidheat exchanger to the upper portion of said stor-' age vessel; and pumpmeans adapted so as to maintain pressure on liquid recycled from saidheat exchanger to said storage vessel.

9. A liquefied gas storage and dispensing system comprising an insulatedstorage vessel; a heat exchange vessel provided with a liquid levelcontrol means; a first conduit communicating between the lower portionof said storage vessel and said heat exchange vessel; a flow controlvalve provided in said first conduit and communi eating with said liquidlevel control; a second conduit communicating between the upper portionof said heat exchange vessel and a gas disposal point; a pressureregulator provided in said second conduit intermediate its ends; a thirdconduit communicating between the lower portion of said heat exchangevessel and the upper portion Of said storage vessel; and a pump providedin said third conduit intermediate its ends.

GEORGE R. BENZ.

REFERENCES CITED UNITED STATES PATENTS Number Name Date Garretson June12, 1945:

